Seasonal Climate Outlook Message for May to August 2001

The bottom line

SOI message 23rd May 2001 The 30-day average of the Southern Oscillation Index (SOI) is -10.2 up to 23rd May 2001. Note that a low negative SOI for the month of May will slightly reduce the current rainfall probabilities across much of the state regardless of whether an El Niño develops.

Using a March/April Consistently Near Zero SOI phase, the chance of receiving at least the long-term median total May-June-July rainfall is between 40 and 50% for most of the state. However exceptions include probabilities of 30-40% in the southern Darling Downs, and 50-70% in parts of the north-west Central Highlands. This forecast will be updated next week.

The full story

Review of Climate Forecasts and Information Climate pattern and SOI 'phase'. Based on the latest values and trends of the SOI, the chance of receiving at least the May-July median is between 40 and 50% for most of Queensland.

There is a belt from inland of Mackay to Richmond where probabilities are slightly higher at 50 to 70%. Southern Qld has regions including Goondiwindi/St George/Surat that have a 30-40% chance of above- median May-July rainfall.

Victoria, SA, and WA mostly have a 40-60% chance of getting at least median May-July rainfall. However the northern reaches of NT and WA have a 60-80% chance of at least their median totals.

Note that a 70% probability of receiving the long- term median for a location also means there is a 30% probability of not receiving the median for that location. These probability values are simply statements of fact referring to the history of rainfall events for particular locations over the past 100 years.

The outlook for winter is dependent on whether or not an El Niño develops during the next 3 months.

Sea-surface temperatures (SSTs). The drop in the average SOI has been accompanied by warming of SSTs in the far eastern equatorial Pacific Ocean; however, it is too early to tell if this will continue to develop into something significant such as an El Niño.

Many general circulation models are suggesting that warming in the eastern equatorial Pacific Ocean will continue over the next 3 to 6 months. We will watch the situation closely to determine any potential for El Niño development this autumn. Close monitoring of SST patterns and the SOI over the next few months is suggested.

Pasture Growth forecasts. The probabilities of obtaining median pasture growth or better during the April-May-June period are very patchy across the state. In the north and in coastal regions there are mostly low probabilities (10%) of 'above-average' growth. However, probabilities are higher (between 50 and 70%) in central and western districts .

30 to 50-Day Oscillation. The 30-50 day oscillation is next due to influence Queensland around the last week of May.